A memory device having a three-dimensional structure has been proposed in which memory holes are made in a stacked body in which insulating layers are multiply stacked alternately with electrode layers that function as control gates of memory cells, and silicon bodies used to form channels are provided on the side walls of the memory holes with a charge storage film interposed between the silicon bodies and the side walls.
In the memory device having such a three-dimensional structure, problems are known in which the memory hole diameter undesirably changes in the depth direction.
The difference of the memory hole diameter may lead to operating characteristic fluctuation due to the surface area of the electrode layer provided around the memory hole undesirably fluctuating between the different levels.